In this study, modified biochar (BRB) was prepared from rice straw by ball milling technique and used for the adsorption of methylene blue (MB) in wastewater. The BRB was characterized by SEM, FTIR and XPS, and the adsorption model and Box–Behnken design were used to optimize the five influencing factors. The results showed that the ball milling technique could increase the content of functional groups (–OH, C=C and C–O, etc.) and aromatic structures on the surface of biochar, thus facilitating the removal of MB. The isotherm model was consistent with the Langmuir adsorption model (R² = 0.947) and the maximum adsorption capacity was 50.27 mg/g. The adsorption kinetics was consistent with the pseudo-second-order kinetic model (R² = 1) and the adsorption rate was mainly controlled by chemisorption. The thermodynamic model confirmed that the adsorption process was a spontaneous heat absorption reaction. The maximum adsorption efficiency was 99.78% under the optimal conditions (40℃, pH 8, reaction time = 90 min, dosing amount = 0.1 mg), and the adsorption efficiency could be improved by increasing the pH and BRB dosing amount. The surface functional groups and crystal structure properties of BRB were the main determinants of adsorption, and it was clarified that physical adsorption, electrostatic attraction and π-π interaction were the main mechanisms for the adsorption of MB by BRB. The main mechanisms were clarified. Therefore, BRB is an economic, efficient and green adsorption material with good potential for the removal of dye pollutants in the aqueous environment.

Inductively coupled plasma mass spectrometry (ICP-MS) was used to detect heavy metals in 74 typical and representative commercial organic fertilizers (COFs) collected in major COF production areas in China. The potential risk of fertilization into soils was evaluated. The concentrations of heavy metals (mg kg^− 1) in these COFs were 1.55–36.95 (As), 0.04–2.32 (Hg), 1.43–78.05 (Pb), 0.15–7.49 (Cd), 11.03–212.90 (Cr), 7.74-555.11 (Cu), 21.46-2705.68 (Zn), and 5.62-244.47 (Ni), respectively. Based on China’s Organic Fertilizer Standard (2021), COFs with excessive heavy metals accounted for 45.95% (As), 1.35% (Hg), 2.70% (Pb), 8.11% (Cd), and 6.76% (Cr). According to the European Union standard (2019), the rate of COFs with excessive heavy metals was 32.43% for Cu, 75.68% for Zn, and 85.14% for Ni. Estimated by applying 3854 kg hectare^− 1 (dry bass) of fertilizer per hectare per year, to guarantee the safe use of organic fertilizer, the risk monitoring of Cd in soil should be emphasized. China should formulate appropriate standards for the limits of Cu, Zn, and Ni in organic fertilizer as soon as possible and should pay great attention to heavy metal pollution of soils.

Aims Phosphorus (P) is a finite resource and inoculation of phosphorus‐mobilizing bacteria (PMB) is a promising approach for the enhancement of soil P availability and plant P uptake. This drives scientists to search for the microbes effective in mobilizing legacy P in soils. Methods and Results The current incubation and greenhouse pot experiments were conducted to investigate P mobilization and pepper P uptake as affected by a new biocontrol and bioremediation bacterium Burkholderia cepacia CQ18. This bacterium converted Ca₃(PO₄)₂, FePO₄, AlPO₄, and lecithin into soluble inorganic P in the culture solutions and increased available P (including water‐soluble P and Olsen P) in the soil. There were positive correlations between the soluble inorganic phosphorus and the exudates (protons, organic acids (oxalate and gluconate), siderophores and phosphatases) in culture solutions. Pepper plant biomass, fruit yield and P uptake changed in the sequence: chemical fertilizers plus bacterial inoculant > only chemical fertilizers > only bacterial inoculant > blank control. Conclusions Taking into account the wide spectrums of P mobilization and simultaneous production of acid, neutral and alkaline phosphatases at a given pH, B. cepacia CQ18 may be a potential PMB used in soils with wide pH ranges. The mechanisms employed by this bacterium in the solubilization of recalcitrant inorganic P could be the efflux of protons, organic acids (oxalate and gluconate) and siderophores. Phosphatases could be of utmost importance in the mineralization of the organic P. The production of siderophores and phosphatases by of B. cepacia CQ18 could thus be crucial for not only the antagonism against plant pathogens but also the mobilization of soil sparingly available P. Significance and Impact of Study B. cepacia CQ18 could be potentially developed into a biofertilizer.

The self-digestive solution (SDS) of the biocontrol bacterium Lysobacter enzymogenes LE16 shows strong antagonistic activities against multiple soil-borne phytopathogens but the positive evidence of this bacterium against plant foliar disease is still scanty. Thus, laboratory, greenhouse, and field experiments were carried out to estimate the efficacies of SDS, S-SDS (stored at room temperature for 12 months), and H-SDS (heated at 100°C for 30 min) against plant powdery mildew. This bacterium produced hydrolases (phosphatase, protease, lysozyme, chitinase, and β-1,3-glucanase) that degrade pathogen cell components and siderophores that compete for iron with phytopathogens. The top five antimicrobial metabolites identified in SDS were pyroglutamic acid, deoxycytidine, pyrrole-2-carboxylic acid, 13-oxo-9,11-tridecadienoic acid, and 3’-amino-3’-deoxythimidine. Among them, pyroglutamic acid may play a vital role in powdery mildew control. As a result, SDS, S-SDS, and H-SDS strongly inhibited the conidial germination of Erysiphe cichoracearum and Sphaerotheca fuliginea. The application of SDS significantly increased the activity of antioxidant enzymes in crop leaves and effectively controlled tobacco and cucumber powdery mildew in the greenhouse and the field. Therefore, L. enzymogenes LE16 can effectively control powdery mildew. The underlying mechanisms may be attributed to the induction of plant systemic resistance and the production of antifungal substances.